The present invention relates to a method for manufacturing multicolored plates such that the surface of a substrate is divided by different colors. The present invention especially relates to a method for manufacturing multicolored plates having fine and close pattern.
The present invention also relates to a method for manufacturing a multicolor display device using a color filter.
One coventional method for manufacturing multicolored plates includes a coloring method utilizing surface diffusion of metal ion known as the so-called staining method, another coloring method comprises the printing and burning of low melting temperature glass frit and another coloring method utilizes printing ink containing organic polymer binder.
However, these conventional methods have various drawbacks. For instance the coloring method by printing has the drawback that the color layer is quite uneven and lacks in clarity and therefore is not a good color layer. The staining method also has the drawback that the fabrication process is complicated by using strong heat and that the possible color tone is restricted though the surface of the substrate keeps its initial smoothness. In addition, these methods have the common drawback in making a fine multicolor pattern that they lack accuracy and at most achieves only some hundreds .mu.m of accuracy and that colors of different tones are mixed with each other at the boundary where the two different colors are divided in two portions.
Also known is a method for manufacturing multicolored plates by coloring anodically oxidized aluminum film which has the good points of smoothness of the colored layer, wide variaty of possible color tone and easy fabrication. This method is applied for various purposes. This method comprises the steps of forming a thin film of aluminum on a base plate, changing this thin film of aluminum into a thin film of anodically oxidized aluminum by an anodically oxidizing method, coloring this thin film of anodically oxidized aluminum by organic or inorganic coloring materials and thereafter sealing the porosity on the surface of the anodically oxidized aluminum thin film so as to stabilize the colored layer. Thus the multicolored plate is quite easily obtained by the above introduced fabrication process.
However this method has to employ the photo-resist method or the sublimate transferring method utilizing thermal sublimation of a sublimate dye so as to divide the anodically oxidized aluminum thin film into different colors. The former method has the drawback that repetition of the photolithography process is required for the different number of color tones and that the fabrication process is complicated. The latter method has also the drawback that the possible color tone is limited due to a limited variety of the sublimate dyes and that a quite fine pattern is hard to obtain according to this method.
FIG. 1 shows an example of a conventional multicolor display device using a color filter. Numeral 1 is a transparent substrate, 2 is a transparent electrode on which a desired figure or letter is patterned, 3 is a color filter, 4 is a second transparent electrode, and 5 is a counter substrate. In a display cell of the above construction, a display material which acts as an optical shutter, such as liquid crystal, electrochromic material or the like, is sandwiched and held between the transparent substrate 1 and the counter substrate 5. Viewing from the direction of the transparent substrate 1, when the shutter "opens", the color of the color filter 3 is displayed; while, when the shutter "closes", the color of the color filter 3 is masked and not shown. Accordingly, when the three primary colors are selected for the color filter, such as, for example, 3a(red), 3b(Green), and 3c(blue) in FIG. 1, and the three primary colors are periodically patterned in a repeating manner, a multicolor display can be made on a single cell. More specifically, to display red, only the optical shutter on the red pattern 3a "opens" and the optical shutters on 3b and 3c "close". To display yellow, the optical shutter on the red pattern 3a and the green pattern 3b "open", and the optical shutter on the blue pattern 3c "closes". In the latter case, yellow is displayed by additive color mixture. If the color filter 3 has an appropriate light transparency and the counter substrate 5 is transparent, a similar effect is obtained if a luminous display material is sandwiched and held between the transparent substrate 1 and the counter substrate 5 and viewed from the direction of the counter substrate 5.
As illustrated, a multicolor display using a color filter is a simple method, and is used for various purposes and has a great effect. Actually, however, in manufacturing a multicolor display device with a color filter, it is difficult to coincide the pattern of the transparent electrode with the pattern of the color filter. The more fine and multicolored the patterns, the more difficult it becomes to coincide the patterns. The color filter can be formed by means of screen printing, photolithography or the like. In the case of screen printing, however, a pattern can not be so finely made. Namely, the more the pattern is multicolored, the worse the precision of the printing portion is, and color shear occurs. In the case of photolithography, a pattern can be made fine, but the processes are extremely complicated since the photolithography process is needed whenever the color changes. This is inconsistent with the advantages of the color filter; that is, the simplicity and capability of multicolor display.